Federal health officials are warning the public about a version of synthetic marijuana laced with rat poison that's caused uncontrolled bleeding in hundreds of people and killed several others who have ingested the tainted products.

The synthetic cannabinoid, sold under names such as Spice, K2 and AK 47, has hospitalized people in 10 states since early March. That's when health officials in Illinois discovered people at hospital emergency rooms with severe bleeding had ingested synthetic marijuana laced with brodifacoum, a lethal anticoagulant found in rat poison.

A bad batch appears to be circulating in Washington D.C., where fire and emergency medical crews suspect the substance in 210 cases since Saturday involving severe nose bleeds, vomiting and people collapsing. Of those cases, 150 people have been sent to area hospitals, according to Doug Buchanan, a spokesman for Washington D.C. Fire and EMS.

Although synthetic marijuana has been sold for years at gas stations, convenience stores and smoke shops, federal health officials and law enforcement said this version is particularly alarming.

In a public health alert released Thursday, Food and Drug Administration Commissioner Scott Gottlieb and two other high-ranking agency officials warned the public to avoid any version of synthetic marijuana.

"We’re joining together to send a strong warning to anyone who may use synthetic marijuana products that these products can be especially dangerous as a result of the seemingly deliberate use of brodifacoum in these illegal products," the FDA officials' statement said.

The FDA officials said there's "significant public health concern" for people who smoke synthetic marijuana and the U.S. blood supply. At least three people in Illinois donated blood before they were hospitalized for using tainted synthetic marijuana, according to an earlier Centers for Disease Control and Prevention clinical alert.

Synthetic marijuana listed in the same category as street drugs such as LSD and cocaine, but marketers label packages "not for human consumption" or change the chemical structure to skirt legal requirements, according to the FDA.

Officials said the illegal drugs are associated with adverse health effects such as rapid heart rate, vomiting, increased blood pressure, reduced blood supply to the heart, kidney damage and seizures. Users also have exhibited violent behavior or expressed suicidal thoughts.

Health officials and law enforcement believe makers of the product have mixed batches with brodifacoum, or BDF, an ingredient found in the current wave of people suffering from uncontrolled bleeding.

On May 25, state health departments reported 202 cases and five deaths involving patients who needed treatment for severe bleeding after ingesting synthetic marijuana, the CDC reported.

The Washington D.C. medical examiner's office is investigating another four deaths since Saturday, but officials have not yet confirmed whether those casualties involved BDF or other substances.

Another 33 cases and one death have been confirmed in Maryland, according to the Maryland Poison Center.

The presence of BDF in synthetic marijuana is troubling because of the substance's powerful and long-lasting effect, experts said.

Douglas Feinstein, a University of Illinois researcher who has received National Institutes of Health funding to study the effects of BDF, said the substance is essentially a much more powerful, deadly version of the anti-clotting drug warfarin.

He said it was developed as a poison to kill rats and mice who became resistant to milder versions of anti-clotting agents.

Drugs and agents that include BDF "are not for human consumption," Feinstein said.

While health officials do not know why BDF is surfacing in synthetic marijuana, Feinstein said one possible explanation is that the substance effectively slows a body's ability to metabolize the drug. That could make the drug's "high" last longer.

Another theory is that the substance is being inadvertently put into the chemical mix when it's made abroad. A more sinister possibility is that makers of the drug intentionally mixed BDF into the product, according to Feinstein.

Health officials said people who have used synthetic marijuana should monitor carefully for any signs of bleeding. People who have used the BDF-laced synthetic marijuana have reported easy bruising, oozing gums and nose bleeds, according to the FDA.

Officials said people who are experiencing the systems should immediately seek medical care because the effects of BDF are treatable. People can get oral doses of Vitamin K to counteract the effects of the substance. It costs $8,000 for a two-week course of Vitamin K on an outpatient basis, but people poisoned by BDF may need months of treatment, according to the CDC.

Bruce Anderson, executive director of the Maryland Poison Center, part of the University of Maryland College of Pharmacy, said the current scare is the latest in a long list of adverse health effects of people ingesting synthetic marijuana.

"The reality is people are using these products on a regular basis," Anderson said. "Some people are happily getting high but there are consequences. Sometimes, fatal consequences."

Anderson said people who use synthetic marijuana may be doing so to avert drug screens that test for more commonly-used street drugs like marijuana or cocaine. Professional football players like former New England Patriots defensive end Chandler Jones and ex-Seattle Seahawks fullback Derrick Coleman were linked to the substance before the National Football League added synthetic marijuana to its list of banned substances.

One of the Maryland patients recently harmed by BDF used synthetic marijuana to avoid a positive drug test, a risky proposition considering people don't know what may be mixed in any particular batch, said Anderson.

"Not only is it (synthetic marijuana) deadly toxic all by itself, it's sort of playing Russian Roulette," Anderson said. "You could end up getting stuff that contains brodifacoum."